Hello,
My ISP asked me to replace my modem with a newer one and let me keep the old one. So now I have this device on my desk and I may as well try to do something with it.
It is an SFR NB6V-FXC-r0. At first I thought it was https://openwrt.org/toh/hwdata/sfr/sfr_neufbox6 because the case is similar and the model name only has an extra 'V' in it but it turns out (after connecting an UART to it, the connector is easily available on the back of the device under a "warranty void" sticker) it is in fact quite different hardware.
It is a bcm63168, and there seem to be some supported devices using this chip, I think? It also has more RAM (128MB) and flash (64MB) than the previous generation, which seems enough to do some interesting things.
With my UART I have access to the CFE bootloader. I also have access to what looks like a Linux with Busybox if I let it boot, but it asks me for a login/password and I don't know what that would be.
So, where do I go from there? Is it hope to get it working relatively easily (I'm not afraid of having to compile a few things from sources and do some hacking on it) or will it need years of reverse engineering and writing drivers?
Thanks for your help 
It depends on what you would like to get working. If it has a DSL modem, this won't work as there is no open source driver. If the WiFi is Broadcom, it will either not work at all or it will perform very poorly due to the limitations of the open source drivers.
In fact, we try to avoid Broadcom as much as possible.
I will be happy enough if I get OpenWRT installed and the ethernet, USB, and maybe the LEDs and buttons working. I don't need the DSL (I don't have a hponeline anymore) and I don't really need the Wifi even if it would open a few more possible uses.
OK, then you can have a look at the developer guide in the Wiki: https://openwrt.org/docs/guide-developer/start
Before I start building and attempting to flash something on it, I think it would be nice to dump the existing firmware? So I have at least some chance to get back to that if I break everything, and also so I can explore what's on it (I guess I should find a device tree or something like that? although it says it's Linux 2.6 in the boot log, so that may be too old for device trees, so I'll have to find out how to extract hardware info from pre-device tree Linux).
Here is a log from the serial console during boot: http://pulkomandy.tk/drop/nb6v-bootlog.txt
And a few CFE commands I can run: http://pulkomandy.tk/drop/cfe-commands.txt
I see that CFE has a "run from host" command, can this be used to boot something from TFTP without flashing it on the device? Is there documentation somewhere on using that? If this can be made to work I think it would be quite convenient for development and possibly for exploring what's on the device.